Tuesday, March 6, 2012

New research on Pikaia from Simon Conway Morris and Jean-Bernard Caron.

In Pikaia gracilens Walcott, a stem-group chordate from the Middle Cambrian of British Columbia, published online March 4, 2012, Simon Conway Morris and Jean-Bernard Caron confirmed that Pikaia was a chordate after all. They looked at the anatomy of 114 specimens of Pikaia (I thought there were only 16 known Pikaias!)and found myomeres, v-shaped blocks of skeletal tissue that are only found in chordates. The scientists also found evidence of a vascular system, and found that at least part of the alimentary canal was preserved in almost every specimen.

Externally, Pikaia was mostly just a flattened, tie-shaped body tapering from a tiny head. It had tentacles on its head, two antennae, and a thin dorsal fin.

What was first thought to be the notochord in Pikaia is now interpreted as a "dorsal organ," which was possibly hollow. This doesn't mean there's no notochord. Under this dorsal organ there is a thread of tissue that is now interpreted as the notochord and nerve chord.

I've only read the abstract, but when I read the actual article I'll learn more information.

5 comments:

I've been wondering about this, and you might know: Is it known if Pikaia's brain was wired up to its body contralaterally (left brain controls right body and vice versa) like in humans and other modern chordates? Or do the fossils not preserve neural material well enough to tell?

Here's a link to an article on blog which has the full details of the discovery if you have still not been able to access the researcher paper online:http://prehistoricict.blogspot.com/2012/03/oldest-vertebrate-on-earth.html

Note From the Typist

Art started writing this blog at age seven and completed the majority of the work before he turned nine. He did his own research and for a long time dictated the blog entries to me, his mother. I typed exactly what he said and did my best to spell everything correctly.

For a glimpse into the early blogging process, check out the video below.